35 amp ish at 15v ish power supply? Diy anodising!

[GraemeVW]

Having idle thoughts about some home aluminium anodising.
Local anodisers don't want the job, so looking into what's involved.
It needs a tank about 1mx1mx0.5m so quite a bit of electrolyte too.
But the power supply might be the main sticking point. Probably about 1200 square inch of surface area which will need about 35 amp I believe. So my little 5a bench psu is out.
I believe you use around 15v?
Any thoughts on what I could use to provide this? My initial thought was if it would be possible to use an old welder of some description.

Probably a bit of a step too far to be trying to anodise large items at home, but didn't want to dismiss the possibility without looking into it first.

 

[brightspark]

ac or dc i have a heavy 12volt ac transformer of a string of lights

 

[Ubique]

A Lead-Calcium battery charger will run about 14.8 - 15.2V and 35A isn't an excessive rating - not sure how you'd pursuade it there's a battery connected though as all the regulation is electronic, not transformer based

 

[GraemeVW]

ac or dc i have a heavy 12volt ac transformer of a string of lights

A very good question, and quite important. I dont know! Id assume dc though.

Edit, just checked, yes dc.

 

[hotponyshoes]

It's not impossible to do it at home. I was doing it years ago with decent success (after a lot of fiddling)
I was doing hard coat at 6a/1'sq not huge parts but was running a few at once. I ended up with a 100a 70v dc power supply. Still got it and would sell it if you can collect. Its not massive but too heavy to shift by carrier.

Ideally you want a constant current power supply so you set the amps required and then the supply needs enough headroom on the voltage to maintain the amps.
The voltage required will depend on the tank solution/temperature/etc but 15v sounds too low to me (but do the maths and check as it's been a while since I did any)
All the diy methods using car chargers, 5 laptop supplies joined together etc etc work to a fashion. Some work better than others. For one big piece as a one off job you'll probably get away with anything. You can even just use battries if you want.
But if it's any sort of repeat job and you want any sort of consistency then constant-current is the way to go.

You can make the bath to suit the size of the item if it's a one-off so you don't need loads of expensive acid but the bath will heat up pretty quickly on a big item so the bigger the better really.

 

[Robotstar5]

What about a radio power supply? 30A and 9 - 15VDC - Link

 

[GraemeVW]

It's not impossible to do it at home. I was doing it years ago with decent success (after a lot of fiddling)
I was doing hard coat at 6a/1'sq not huge parts but was running a few at once. I ended up with a 100a 70v dc power supply. Still got it and would sell it if you can collect. Its not massive but too heavy to shift by carrier.

Ideally you want a constant current power supply so you set the amps required and then the supply needs enough headroom on the voltage to maintain the amps.
The voltage required will depend on the tank solution/temperature/etc but 15v sounds too low to me (but do the maths and check as it's been a while since I did any)
All the diy methods using car chargers, 5 laptop supplies joined together etc etc work to a fashion. Some work better than others. For one big piece as a one off job you'll probably get away with anything. You can even just use battries if you want.
But if it's any sort of repeat job and you want any sort of consistency then constant-current is the way to go.

You can make the bath to suit the size of the item if it's a one-off so you don't need loads of expensive acid but the bath will heat up pretty quickly on a big item so the bigger the better really.

It's a motorcycle frame. Would very much be a one off. I'd do swing arm and wheels too. I've done a fair bit of home electroplating, but no anodising.

The parts will be polished, I was looking to clear anodise after so I don't have to keep polishing them. Local anodisers were sounding very positive until they realised the parts are hollow. They were worried about draining them, even though they have holes, and contaminating the tanks.
Hence me now seeing how viable it would be to do at home!

I only did a quick Google about current and it said 0.03a per 1" square at 16v. But I assume that's small parts, a frame with (VERY rough guess, 1200 square inch) might be a different ball game.

At the moment, if it looks like it might be doable without huge outlay for a 1 off job, then I'll use my small tanks and psu to practice on small parts before diving into setting up to do the frame.

 

[GraemeVW]

What about a radio power supply? 30A and 9 - 15VDC - Link

I have no idea! Might work...

 

[Chippie]

Take a microwave oven transformer, remove the hf winding rewind with cu wire (flat bar?) …..maybe?

 

[hotponyshoes]

It's a motorcycle frame. Would very much be a one off. I'd do swing arm and wheels too. I've done a fair bit of home electroplating, but no anodising.

The parts will be polished, I was looking to clear anodise after so I don't have to keep polishing them. Local anodisers were sounding very positive until they realised the parts are hollow. They were worried about draining them, even though they have holes, and contaminating the tanks.
Hence me now seeing how viable it would be to do at home!

I only did a quick Google about current and it said 0.03a per 1" square at 16v. But I assume that's small parts, a frame with (VERY rough guess, 1200 square inch) might be a different ball game.

At the moment, if it looks like it might be doable without huge outlay for a 1 off job, then I'll use my small tanks and psu to practice on small parts before diving into setting up to do the frame.

Sounds too low.
You would be ok at that for colour dye (although it's going to take a long time) but to get a decent clear finish you really want to be heading towards the 10a-12a/sq' at a minimum.
If it's just for protection or a base for paint then it should be fine but if you want to keep any resemblance of a polished finish you want to have it in the bath for the shortest possible time and keep the pores really tight to keep it looking shiny

 

[hotponyshoes]

Certainly worth having a practice on a smaller scale first. Especially for clear.
Then you can see just how much difference the bath time makes and just how much power you need.
And see if you are happy with the finish you can achieve.

You also have more chance of a perfect finish on clear doing it diy as the commercial baths are never normally that clean.
If the people you spoke to are worried about contaminating the bath then I expect they are one of the better places!
If you find a place that is happy to just chuck it in odds are it won't come back as nice looking as you would hope for anyway!

 

[GraemeVW]

Take a microwave oven transformer, remove the hf winding rewind with cu wire (flat bar?) …..maybe?

Sounds like if needs more knowledge than

Sounds too low.
You would be ok at that for colour dye (although it's going to take a long time) but to get a decent clear finish you really want to be heading towards the 10a-12a/sq' at a minimum.
If it's just for protection or a base for paint then it should be fine but if you want to keep any resemblance of a polished finish you want to have it in the bath for the shortest possible time and keep the pores really tight to keep it looking shiny

Ok, so let's call it 10 square foot, so I'd need 100a, ish.
What kind of voltage?

I ca , on a small scale, practice on some polished bits of aluminium, try and get to a point where I understand the variables and just (JUST!!), need to scale it up. ALOT.

 

[GraemeVW]

Certainly worth having a practice on a smaller scale first. Especially for clear.
Then you can see just how much difference the bath time makes and just how much power you need.
And see if you are happy with the finish you can achieve.

You also have more chance of a perfect finish on clear doing it diy as the commercial baths are never normally that clean.
If the people you spoke to are worried about contaminating the bath then I expect they are one of the better places!
If you find a place that is happy to just chuck it in odds are it won't come back as nice looking as you would hope for anyway!

They were a decent company, doing all kinds of anodising work. 2m tanks too.
Interesting that I may even be better off doing my own.
I'd deffinately practice, just wanted to get a feel of if I'd be practising for no reason if I couldn't scale up.

100a is making me wonder if I could use my old mig welder as a power supply.

 

[hotponyshoes]

You need whatever volts it takes to maintain 100a. Ie, a lot.

The stronger the acid solution (ie the more conductive the bath) the less volts you need. Thinner coating = less volts, hotter bath = less volts and so on.

But, running the bath colder will keep the polished alloy shiner so it's all a trade-off

 

[GraemeVW]

You need whatever volts it takes to maintain 100a. Ie, a lot.

The stronger the acid solution (ie the more conductive the bath) the less volts you need. Thinner coating = less volts, hotter bath = less volts and so on.

But, running the bath colder will keep the polished alloy shiner so it's all a trade-off

I should know that from plating. Never even look at the voltage, it just is what it is.

Good info there, thanks. I'll have a play.
What were you using for acid? I have a few car batteries but that was before I was thinking about this size tank!

 

[hotponyshoes]

They were a decent company, doing all kinds of anodising work. 2m tanks too.
Interesting that I may even be 100a is making me wonder if I could use my old mig welder as a power supply.

If you can come up with some sort of hole system that they are happy with then sounds like they would be an easy way.
Decent places don't like stuff where they can't see every surface though and getting the inside of a bike frame to anno correctly would be a challenge. I'd think a good company would turn the job down as they can't be sure it will turn out to the standard they would like.

A mig is constant voltage.
Ideally you would use a tig as that's constant current.

 

[GraemeVW]

If you can come up with some sort of hole system that they are happy with then sounds like they would be an easy way.
Decent places don't like stuff where they can't see every surface though and getting the inside of a bike frame to anno correctly would be a challenge. I'd think a good company would turn the job down as they can't be sure it will turn out to the standard they would like.

A mig is constant voltage.
Ideally you would use a tig as that's constant current.

Yeah, it's a shame they said no. They knew what they were talking about and didn't see the job as a problem
They warned me the welds will look different, and may get streaks where it runs from the holes. I think though, unless it's rotated when removed from a tank it will always trap a fair bit of liquid.

I will ask a few other anodisers though, before I give up on getting it done professionally.

If I could use a tig welder, without killing it, that would be another good excuse to buy a cheap one. Might not like being used constantly though, duty cycle etc.

 

[Misterg]

let's call it 10 square foot, so I'd need 100a, ish.

6A / sq ft for 2 hours will give a decent layer (~~25µm).

You can use sodium bisulphate instead of sulphuric acid. It's more readily available (sold as swimming pool pH down).

Voltage depends on temperature as well, but I guess you'd need ~20V on tap to be safe. (Ideally constant current, as above).

Has it been anodised before? If so, it'll need stripping (in sodium hydroxide) before re-anodising.

 

[hotponyshoes]

I should know that from plating. Never even look at the voltage, it just is what it is.

Good info there, thanks. I'll have a play.
What were you using for acid? I have a few car batteries but that was before I was thinking about this size tank!

Sulphuric at 25% with distilled water. It's basically car battery acid but if you buy it raw and mix it you know what ratio it is.
I used car batterys as a source for my trial runs just by sticking it through a coffee filter to get the crud out. Friendly scrap yard will be happy enough for you to drain all their batteries out as long as you take the lead back!
Again, you won't know if all the concentrations are the same so will be harder to translate a test run to a full run. Ideally you would mix the big bath first then take some back out to do the testing.
But I never messed around with the ratios that much.. I don't think high accuracy is vital. A refractometer reading should be good enough I'd think.

 

[hotponyshoes]

6A / sq ft for 2 hours will give a decent layer (~~25µm).

You can use sodium bisulphate instead of sulphuric acid. It's more readily available (sold as swimming pool pH down).

Voltage depends on temperature as well, but I guess you'd need ~20V on tap to be safe. (Ideally constant current, as above).

Has it been anodised before? If so, it'll need stripping (in sodium hydroxide) before re-anodising.

6a/2hrs would look quite a lot duller than 12a/1hr. (only really talking about clear coat)
Do some scaled-down tests as you might find you don't like the look of it at all if you go below 24a/30mins.

Or, make things easier and don't go for polished. Soda/vapour blasted or something first would make things a lot easier. Just needs to be some sort of treatment where you can be 100% sure you have removed 100% of the blast media.